A baler, particularly of the type producing large cylindrical bales, has a compaction chamber to which a stream of crop is delivered continuously, normally entering via a hole in the upstream end of the floor of the chamber. Compacting organs press together the crop, pushing it downstream from the intake opening, and when the bale is fully formed needles poke crosswise across the path of the strand behind the compactors to pass a tie around the trailing end of the bale.
The typical such press as described in East German patent document No. 112,066 has a reciprocating piston which is formed with a plurality of slots extending in its displacement direction and opening at the face used to push and compress the crop. Once the piston is pushed up against the trailing end of the bale the strand-guiding needles of the tying device move up through these slots to pull the strands, which normally are either wire or string, around this trailing end, whereupon a knotting device can tie them off, that is can cut each strand and tie the cut end with the previously cut end. Operating synchronously with the piston is a cutter which slices through the crop stream at the lateral intake opening just as the piston moves past it, this intake being blocked by the piston during the final compaction/tying operation.
Such a system has the disadvantage that sliding through the crop stream is a relatively difficult operation that puts a relatively large temporary load on the drive for the baler. Thus this drive must be overdimensioned to take up this periodic large load. In addition the complete blockage of movement of the crop for the relatively long period of time it takes to tie up the bale and retract the piston can cause the crop to jam in the passage leading to the intake opening.
The arrangement of West German patent document No. 3,241,490 is a large round-bale machine which compacts the crop with a pair of forks that engage in the crop stream and push it back, and that on their return stroke to the front of the device are pulled laterally out of the crop stream. In this system the tie-guiding needles push up through the relatively loose crop stream in back of the compaction forks. The disadvantage of this arrangement is that pushing the needles through even the relatively loose crop is difficult so that the ties can break. Furthermore the crop in the bale and the crop in the stream still remains somewhat joined past the ties, so that when the bale is ejected it entrains some of this crop and can break the ties and needles.
In another machine proposed in West German utility model No. 7,521,769 the tie needles pass through the crop at the extreme downstream end of the chute at the intake mouth of the baling chamber. Segmental shields block this chute immediately upstream of these needles to protect them as they traverse the chute. Such a device once again demands that the movement of the continuously arriving strand of crop be blocked for enough time to make jamming likely and to interfere with continuously picking a windrow of the crop up off the ground. In addition it is only applicable to large round-type balers that do not have particular compaction elements.
Yet another system is known from West German patent document 2,647,472 where the needles also pass through the crop stream right where it enters the compaction chamber. Here special shield rails are provided to protect the tie needles. Such a system can have blocking combs that, once again, completely block passage of the crop into the compaction chamber, so that jamming of the machine is likely.